title: Dynamics of imprinted DNA methylation and gene transcription for imprinting establishment in mouse oocytes in relation to culture duration variability.
abstract: Several studies have linked assisted reproductive technologies to aberrant imprinting. We previously showed that 12-day in vitro follicle culture supports normal imprinting establishment in mouse oocytes. The aim of the present study was to assess whether shortened in vitro follicle growth (8 days of culture compared with 12 days, as a model for human in vitro maturation) or preovulatory intrafollicular oocyte "aging" in culture (14 days of culture) leads to imprinting mutations in oocytes. Limiting-dilution bisulphite sequencing showed that shortened in vitro follicle growth (8 days) does not induce oocyte epimutations at the imprinted Snrpn and Mest genes. In contrast, extension of oocyte residence in large unluteinized follicles in vitro was associated with a low level (1 of 54 alleles) of epimutations for Mest but not for Snrpn. The latter condition may occur during controlled ovarian stimulation where the oocyte growth phase may be extended for several days. Furthermore, we studied the dynamics during follicle culture of transcript levels for genes previously shown to be essential for imprinting establishment in oocytes, including Dnmt3a, Dnmt3L, and Zfp57. Oocyte total mRNA levels during in vitro follicle culture showed the timely shutdown in transcription at the antral follicle stage, and total mRNA levels were comparable to those of in vivo grown equine chorionic gonadotropin-stimulated oocytes.
authors.affiliation: Follicle Biology Laboratory, Vrije Universiteit Brussel, Brussels, Belgium.
authors.forename: Ellen
authors.initials: E
authors.lastname: Anckaert
authors.forename: Flor
authors.initials: F
authors.lastname: Sánchez
authors.forename: Katy
authors.initials: K
authors.lastname: Billooye
authors.forename: Johan
authors.initials: J
authors.lastname: Smitz
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019175:DNA Methylation; D005260:Female; D018392:Genomic Imprinting; D059471:In Vitro Oocyte Maturation Techniques / Q000379:methods; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D009865:Oocytes / Q000378:metabolism*; D009866:Oogenesis / Q000235:genetics; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D055517:snRNP Core Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D011506:Proteins; C103637:mesoderm specific transcript protein; D055517:snRNP Core Proteins
keywords: DNA methylation; follicle culture; genomic imprinting; oocyte maturation; total mRNA